The present invention relates to a corneal surgical apparatus for incising the cornea of patient's eye in a layered form in keratorefractive surgery or photorefractive keratectomy (PRK).
In recent years, attention has been focused on LASIK (laser in situ keratomileusis) for effecting keratomileusis (keratorefractive) treatment wherein after a flap is formed by incising a corneal portion of 150 .mu.m thickness ranging from the corneal epithelium to the corneal stroma with one end of the corneal portion remaining connected like a hinge, the corneal stroma is cut away or ablated in a refractive correction amount by Excimer laser light, and the flap is returned to its original position. In this surgery, a corneal surgical apparatus called microkeratome is used to incise the cornea in a layered form. So called "upper hinge flap method" in which the hinge is formed on the upper side (upper eyelid side) of the patient's eye is effective to prevent the deviation and the like of the flap during adhesion of the cornea after the surgery is complete, and thus generally adopted to the PRK recently.
A typical microkeratome includes a suction unit for vacuum-adhering a corneal surface, a cornea applanating member for applanating a corneal portion projecting from an opening portion of the suction unit, and a blade linearly moved in the direction toward the hinge while being oscillated in the lateral direction so as to incise the applanated corneal portion into a layered form with a substantially uniform thickness.
In addition, in recent years, there has been proposed a microkeratome having a blade which is pivoted by using a single pivotal axis as its reference while oscillating the blade so as to form a hinged flap.
Each of these microkeratomes are designed to make oscillation of the blade for incision of the relatively hard Bowman's membrane underlying the corneal epithelium (particularly for the start of the cutting), but is disadvantageous in that a complicated mechanism is required to make the linear motion of the blade (or pivoting motion of the blade with one axis as the reference) while oscillating the blade.
With the type in which the blade is advanced linearly, a feeding mechanism for linearly feeding the blade and a holding mechanism thereof occupy an area in the feeding direction, so that the patient's cheek hinders the formation of the upper hinge flap.
On the other hand, with the type in which the blade is pivoted by using one axis as the reference, since the feeding pitches of the blade differ between the side close to the pivoting axis and the side remote from it, the incision differs depending on the position on the edge of the blade, so that the incised surface tends to be nonuniform.